Portable burglar alarm



F. CRSSMAN. PORTABLE BURGLAR ALARM. FILED Au. 16. 1921 f Dein:vr 26, 1922. 1,440,005.

NVENTOR. /ym//r CROSS/WAM ATTORNEYS.

Patented Dec; Z6, i922.

rnaaa orti rianne Caesarean, or een rnancisco, oanrroaura. y

romania .susanna ALARM.

Application filed August 16, 1921. `Serial No. 492,770.

be conveniently carried in a suit case, can be` quickly attached to any door knob and sounds the alarm when the door knob isy turned in either direction. lt is principally intended for travellers whor frequently 'change their quarters and have to sleep in places not familiar yto them, and provides for them a convenient means `of apprising them of any attempt to open thedoor.

The preferred embodiment `of the principles involved `in my invention is shown in the accompanying drawing, which repre sente a front elevation of my device at' tached to a door knob.

Referringl to the drawing in detail, l wish to state thatV the principle involved in my invention is the use of an electric alarm unit `pivotally depending from the door knob in such manner that it maintains its perpendic-- ular position underneath the door knob ab though the latter is turned, whereby a metallic part of the device is brought in contact withy the door knob and closes an electric circ1| it which soundsthe alarm.

The door (l), of whichonly a fragment is shown in the drawings, has' the door knob (2) attached thereto as in yany ordinary door. It is understood that this door knob has to be revolved in order to open the door. To the latter my electric alarm device (3) is attached by means of the clamp Various fastening means may be used as long as they properly perform the function stated herein. The special clamp shown consists of two metallic `semi-circular members (6) adapted to lit around the knob of the ordinary door and to be tightened on the saine by means of the screws (7) having inilled heads (8) and penetrating perforar-- tions (9) in flanges (ll) of one of the ineinbersand adapted 4"to be screwed into nuts (l2) lixedly secured to registering `flanges of the other member. rlhe clamp members are provided with peripheral flanges (14) to insure a more perfect clamping effect.

From a central portion of the lower clamping member depend two parallel lips `(lh) having` registering perforations and being adapted to receive a perforated projection (18)(1nade of insulating material, of the electric alarm device A screw (19) extending` through the perforations allows the bell arrangement to freely swing on the pivot `parallel to the door.

The alarm device, which is not shown in detail, may beof any desired `form `and includes the two batteries (2l), a bell (22), ak

bell hammer (23) and preferably an electromagnet, an armature and a' vibrator.. The' wiring is easily understood. rlhe circuit leads from the terminal (24) of one of the batteries to the contact (26), from there through the electromagnet and through the `contact spring and contact point not shown in the drawing to the Contact (27) and through the wire (28) to the metallic clamp (6) which is electrically separated from the alarm device through `the insulating project/ion (18). character of the other battery is connected, preferably by av spring' noty shown7 to the metal plate (29) lyingacross the two batteries from which rise two metal screws (3l) in spaced relation. The screws can be screwed into their support whereby their length above the batteries is adjusted and The terminal of lopposite t can be secured in their adjusted position'by the nuts They are so positioned relative to the door knob that a turning of the knob will bring one or the other of them into contact with the clamps and thereby close the circuit which `causes the bell to ring.

The use ot my, device is easily explained. To fasten it to a door knob place the clamps around the same and tighten the screws (7)7 at the same time clamping the end of the wire (28) between the door knob and the clamp. door by turning the door knob the alarm device will remain in its perpendicular posie lf anybody now tries to open the tion but will be raised and moved laterally and the terminalthe other battery.

one of the screw contacts to the plate (29) l0 ineta'llic clamp' secured on the knob having means thereon tor pvotally supporting the de ice, means for insulating the clamp from the letter, a` metallic connection between said source and. the clamp passing through the ringing device, two lateral contacts rising from the latter and extending to Within close proximity ot' the clfinpv on opposite Sides being electrically connected with the source of energy and adapted to engage the clamp When the knob is turned for ringing the bell. n v y FRANK cnoeeitm.` 

